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The parlous state of our air force in the wake of a slew of accidents has been revealed in documents showing commanders stepped back on their ability to carry out missions to deal with emerging safety issues.

The new documents reveal the realisation among military commanders after the fatal Anzac Day crash of 2010 that it had embedded, serious issues that needed to be addressed.

It appears contrary to the public position the military adopted in the wake of the Court of Inquiry into the crash that largely focused on 3 Squadron, home to the three men who died in the 2010 Iriquois crash.

Instead, the documents show the Chief of Air Force at the time, Air Vice Marshall Graham Lintott, detailing safety concerns across the air force and pressure on staff affecting the air force's ability to do its job.

The documents were released through the Official Information Act five years after they were originally sought - and only after the intervention of the Office of the Ombudsman.

The NZ Herald sought the information in 2012 after inquiries into the fatal helicopter Anzac Day crash suggested the problems identified at 3 Squadron - the base for the Iriquois and its crew - existed in other parts of the air force.

A leaked report showed the air force's senior crash investigator stating: "The RNZAF does not have the appropriate and effective processes to adequately and reliably ensure safe and effective military air operations."

The report was among evidence considered by the formal Court of Inquiry into the crash, which touched on the issues raised and recommended an investigation into "broader organisational issues" to avoid future accidents.

The investigation did not occur but the details released through the Official Information Act shows the air force was well aware of the problems with which it was wrestling.

Two weeks after the April 25 2010 crash, the Chief of Air Force at the time, Graham Lintott, told then-Chief of Defence Force, Lieutenant General Sir Jerry Mateparae, "my senior commanders are already looking hard at organisational factors that may have contributed to the recent increase in aircraft accidents and incidents".

Lintott's memo - copied to then-Minister of Defence Wayne Mapp - referred to the Anzac Day crash, a mid-air collision six weeks earlier and a fatal crash in January 2010.

Issues highlighted included the effectiveness of the air force's safety system, its organisation and supervision of flying and training operations and directing resources into improving standards.

Lintott also said there were parallels identified between RNZAF systems and those criticised in the United Kingdom's Royal Air Force inquiry into a fatal crash in Afghanistan that cost 23 lives.

He said the air force would "reduce the risk to safe flying operations by limiting outputs" - cutting back on missions it was expected to carry out. He cited the grounding of the Sea Sprite fleet for five days because of maintenance issues.

Corporal Ben Carson, one of three killed when the RNZAF Iroquois helicopter crashed on April 25, 2010. One crewman, Stevin Creeggan, survived. Photo / Supplied

He said he intended reducing the numbers of helicopters available for the next three years. While the air force could meet its domestic obligations, it would be forced to reduce the aircraft available to assist in the Pacific until the new helicopters were introduced.

Former defence minister Wayne Mapp told the Weekend Herald he was receiving weekly NZDF briefings at the time showing whether individual aircraft were able to be flown.

The attention to detail was driven by the need to be able to advise the Prime Minister - week by week - of what missions the air force was capable of accomplishing.

Mapp said the Anzac Day crash was a "devastating blow" and left senior military leadership " deeply concerned". There was also "deep reflection" over whether the air force was able to do the tasks it had believed it could.

Pauline Carson and Andrew Carson, who are the parents of Ben Carson, a Royal New Zealand Air Force crew member who was killed in a helicopter crash on Anzac Day 2010.

Andrew Carson, who son Ben was killed in the Anzac Day crash, said the documents showed there was an awareness of major safety issues at the time of the fatal flight in 2010.

A spokesman for NZDF said it wasn't possible to answer specific questions relating to the documents, which it had withheld for five years.

However, he said the air force had "learnt the lessons of the Anzac Day accident and still applies these today".

Defence minister Mark Mitchell said "valuable lessons were learned through the comprehensive investigations " that followed the accident.

"The Government takes the wellbeing of our Defence Force seriously, and I have every confidence in the Air Force's safety procedures."

Mitchell said the government was committed to a $20 billion, 15-year upgrade of defence equipment and facilities.

NZ First has promised to hold a public inquiry into the issues which led to the crash if it finds itself in government. The only investigation held into the actual crash has been the military-run inquiry.